The present invention relates to an automatic cocking device in a crossbow for hunting and/or archery.
In known archery and hunting crossbows, one of the main problems is that of their cocking because of the considerable force required to tension the bowstring.
Crossbows are known in which cocking is facilitated by the presence of a ring in the frontal area of the crossbows into which the shooter inserts a foot, so that with the crossbow bearing on the ground and secured by his/her foot, the shooter can pull the bowstring towards him/her with his/her hands until bringing it in the position in which it catches the shooting device associated to the trigger.
However, such a solution is still not very practical and it requires considerable effort on the shooter""s part: in fact crossbows with tensioning exceeding 150-180 pounds (corresponding roughly to 68-82 kg) cannot be constructed.
Another manual cocking system, already used in medieval times, comprises a crank to be operated by the shooter to tension the bowstring by means of reducing mechanisms, but such a solution is operatively complex and the lesser effort required is paid for with an excessively long cocking time.
Moreover, from U.S. Pat. No. 2,520,713 a crossbow is known in which the trigger assembly can translate along the longitudial axis of the crossbow. In a first phase the trigger assembly translates towards the flexing elements to catch the bowstring and in a second phase the operator tensions the bowstring, returning the trigger device to the rear position.
The cocking action therefore takes place manually, acting on the trigger assembly instead of directly on the spring.
Thus, such a crossbow has the drawbacks of a manually cocked crossbow especially as regards the efforts the operator must exert during the cocking phase.
The sole automatic system known to the Applicant is the one disclosed in U.S. Pat. No. 5,220,906 which relates to a device to draw the bowstring of a crossbow, operated by a battery-powered electric motor and housed in a case associated in removable fashion to the crossbow.
The device comprises a shaft which is at least partly threaded and which translates relative to the case on a guide and support walls, actuated by the electric motor.
The electric motor sets in rotation (clockwise or counter-clockwise depending on the position of a switch) a drive shaft whereon is keyed a first gear wheel which meshes onto a second gear wheel mounted on a sleeve having an inner thread which couples with the outer thread of the threaded shaft that translates relative to the sleeve in such a way as to transform the rotational motion of the drive shaft into translating motion of the threaded shaft relative to the trigger of the crossbow. End stop sensors are provided to check the run of the threaded shaft.
However, this solution, which is the only one described in the patent, provides for the rather bulky housing that contains the motor and the battery to be located in the front area of the crossbow in front of the shooting area, in a rather inconvenient position and which, in any case, requires the housing to be removed prior to shooting, both because of the impossibility of releasing the arrow and because the weight of the device on the tip of the crossbow would create an imbalance which would prevent the shooter from shouldering it correctly and from aiming properly.
The patent also mentions the possibility for the device to be positioned in the rear area where the crossbow is shouldered, but it fails to explain in any way how to position it, probably because the inventor did not know how to position it to obtain an effective operation.
Indeed, if the device where actually to be located in the rear part of the crossbow it would have to pull the bowstring (instead of pushing it) during the cocking phase, but the element destined to interact with the bowstring (the slots 74 of the patent) is wholly unsuitable for gripping the bowstring to pull it, as it can only push it.
Moreover, with all traditional bulky elements of the rear part of the crossbow, it is difficult to comprehend a possible installation position of the device which, among other problems, would act in a manner that is not parallel to the shooting axis (as is readily apparent also from FIG. 4 of the aforesaid document).
The lack of parallelism between the action of the automatic device and the shooting axis of the crossbow is a further drawback of the crossbow described in the aforesaid patent and it leads to the following consequences. If the device is mounted anteriorly, it produces a high level of friction of the bowstring against the frame of the crossbow and in particular against the plane whereon the arrow slides during the thrusting phase of the bowstring towards the trigger, whilst if the device is mounted posteriorly it cannot function because it would lift the bowstring relative to the plane of shooting and hence the bowstring could not be properly secured to the trigger.
Although the patent only describes the solution with the removable cocking device (which penalises the shooter who has to mount and remove the device every time he/she shoots), the patent also mentions the possibility for the device to be permanently fastened to the crossbow, but fails to explain how this would be possible and where the device would be fastened. The reason for the many gaps in the patent should be sought in the fact that the inventor probably had thought about some possible variations but without finding any possible embodiment for them and hence without putting a person versed in the art in the condition to construct and embody such variations.
In particular, the aforesaid patent fails to teach how to fasten the device in a permanent manner without influencing the balance of the crossbow and consequently penalising the shooting phase.
In effect, the solution described and illustrated in the patent is ineffective and not feasible for the many problems described above, and in fact as far as the Applicant knows such a solution has never been applied commercially, whilst the other solutions only partially mentioned but not illustrated or fully described (which, a fortiorl, have found no commercial application) do not constitute, in the Applicant""s opinion, prior art.
To the aforesaid drawback one should add the fact that the cocking action is effected directly on the bowstring, thus needing an appropriate fork element destined to interact therewith. This drawback could be overcome by applying to U.S. Pat. No. 5,220,906 the teachings of U.S. Pat. No. 2,520,713, i.e. by having the electric motor act directly on a movable trigger. Such a solution would retain the aforementioned drawbacks, in particular because there would still be a lack of parallelism between the action of the automatic device and the shooting axis of the bowstring, with the aforementioned consequences.
A manually and operable system for cocking the bowstring of a crossbow is disclosed by U.S. Pat. No. 5,823,172, wherein a mechanically operated device for drawing a bowstring with an uniform tension on either side of the crossbow stock is described.
However, such a device has the same drawbacks afore-mentioned about the automatic system disclosed by U.S. Pat. No. 5,220,906.
In particular the cocking device is not an electromechanical automatic cocking device, acts on the bowstring through an inclined fork which can only push and not pull the bowstring and so the device has to be placed on the front edge of the crossbow and has to be removed before shooting.
The aim of the present invention is to eliminate the aforesaid drawbacks and to make available a device for automatically cocking a crossbow applicable to the crosssbow itself in a fixed manner, with no need to remove it every time one shoots.
Another aim is to avoid frictions and jams during the crossbow cocking phase.
A further aim to achieve the above in a simple and reliable manner, without increasing the length or generally the dimensions of the crossbow itself thus avoiding imbalances which would adversely effect the shooting phase.
Said aims are fully achieved by the device of the present invention which is characterised by the content of the claims set out below and in particular in that the trigger block can translate on rectilinear path parallel to the longitudinal axis of the crossbow, in which in a first phase the trigger block advances towards the flexing element until the means for catching and releasing the bowstring automatically catch the bowstring, and in a second phase the trigger block moves back until reaching a position of correct tensioning of the bowstring in which the operation of the trigger causes the instantaneous release of the bowstring, and in that it comprises electromechanical means so shaped as to produce on the trigger block a force substantially parallel to the shooting axis of the crossbow to carry out said first and second phase.
The electromechanical means for automatically tensioning the bowstring comprise an electric motor anchored underneath the crossbow in the area between the trigger block and the butt and powered by a battery preferably housed at the rear part of the crossbow frame or at a grip of the crossbow itself.
The electromechanical means preferably comprise a ball screw whose low-friction rotation causes the movement of a sleeve associated with the trigger block by means of a draw wire sliding on pulleys.
The crossbow can also be provided with a flexing element divided into two halves, each pivotally engaged to the crossbow with the ability to rotate relative thereto in order to be easily made operative by tensioning the bowstring.